Turn development subdomain into client domain

I setup a website in ispconfig 3 on a vps
(ispconfig is on panel.mydomain.com:8080)

Added Web domain dev.mydomain.com is ispconfig
dev.mydomain.com and mydomain.com dns is on my host provider (rackspace) dev.mydomain.com is a cname record
installed wordpress thru aps installer
it all works

now I would like to change dev.mydomain.com to clientdomain.com

I think I update the worpdress site urls first to clientdomain.com, then make A record for clientdomain.com in cloud dns then point clientdomain.com in their registrar to my nameservers?
And in the ispconfig update the web domain entry for dev.mydomain.com to clientdomain.com? and internally it will still point to the folder dev.mydomain.com and it will work or I am I off? OR will changing the Domain field in the web domain entry for dev.mydomain.com mess things up?
Insight much appreciated

brainstorm..
Or do I want to setup a dns zone for clientdomain.com, add new website for clientdomain.com install fresh wordpress , copy over site files to new site, import DB from dev.mydomain.com? only issue how do I view it first to make sure its working before pointing the clientdomain.com from the registrar? This thought occcured to use ispconfig dns so I don;t have to go into rackspace panel